The present invention relates to a combination valve and particularly for secondary air blower in internal combustion engines with controlled three-way catalyzer.
Such combination valves or combivalves which are provided in a valve housing with a by-pass and return valve serve for switching off of the secondary air stream from the exhaust gas pipe of internal combustion engines with controlled three-way catalyzer. A blower, so-called secondary air blower supplies fresh air to the exhaust gas jet of the internal combustion engine as far as possible before the catalyst, for adjusting a post-burning of the exhaust gas at temperatures of above 600.degree. C. operation. With this post-burning the carbon compounds contained in the exhaust gas as well as the carbon monoxide are reduced. Moreover, by the post burning heat is supplied to the catalyzer, and therefore it is specially important for the cold start.
During the operation of the secondary air blower the by-pass valve is open and the secondary air after flowing through the open return valve is blown into the waste gas pipe of the internal combustion engine. The return valve has the function of reducing a return stream of the exhaust gas through the blower during the pressure increase in the waste gas pipe. The by-pass valve prevents suction of the secondary air caused by the pressure pulsation during stoppages of the secondary air blower.
In a known combivalve of the above mentioned general type the actuation of the by-pass valve is performed by the suction pipe negative pressure in the internal combustion engine and the control is executed by an external magnetic valve. The valve member is held in an open position by a valve spring prestressed in an opening direction, and closes when a predetermined suction pipe negative pressure is reached. The closing member of the return valve is formed as a full leaf spring which is inserted at the side of the edge between a valve plate with openings and a stroke catcher.